Cr(VI) Adsorption and Reduction by Humic Acid Coated on Magnetite
Cr(VI) Adsorption and Reduction by Humic Acid Coated on Magnetite
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DOI：
10.1021/es405804m
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发表时间：
2014-07-15
影响因子：
11.4
通讯作者：
O'Shea, Kevin E.
中科院分区：
文献类型：
--
作者：
Jiang, Wenjun;Cai, Quan;O'Shea, Kevin E.
采用易于分离的腐殖酸包覆的磁铁矿（HA-Fe 3 O 4）纳米颗粒有效地吸附并将有毒的Cr（VI）还原为无毒的Cr（III）。在酸性、中性和碱性pH条件下，Cr（VI）的吸附和还原是有效的。铬的吸附符合Langmuir吸附等温式，HA-Fe 3 O 4颗粒对Cr（VI）的吸附符合准二级动力学。通过X射线吸收近边结构谱（XANES）对Cr负载的HA-Fe 3 O 4材料的表征表明，Cr（VI）被还原为Cr（III），而铁芯的价态不变。Fe K边扩展X射线吸收精细结构谱（EXAFS）和X射线衍射测量也表明没有检测到的Fe 3 O 4核心的转变发生在Cr（VI）的吸附和还原。因此，表明HA-Fe_3 O_4表面上的HA负责将Cr（VI）还原为Cr（III）。与HA相关的官能团作为配体，通过偶联还原络合机制形成Cr（III）络合物。Cr K边EXAFS表明，Cr（III）在Cr负载HA-Fe 3 O 4材料中有六个相邻的氧原子，可能在一个八面体的几何形状，平均键长为1.98埃。这些结果表明，易于分离的HA-Fe 3 O 4颗粒具有很好的潜力，去除和解毒的Cr（VI）在水介质中。
Easily separable humic acid coated magnetite (HA-Fe3O4) nanoparticles are employed for effective adsorption and reduction of toxic Cr(VI) to nontoxic Cr(III). The adsorption and reduction of Cr(VI) is effective under acidic, neutral, and basic pH conditions. The chromium adsorption nicely fits the Langmuir isotherm model, and the removal of Cr(VI) from aqueous media by HA-Fe3O4 particles follows pseudo-second-order kinetics. Characterization of the Cr-loaded HA-Fe3O4 materials by X-ray absorption near edge structure spectroscopy (XANES) indicates Cr(VI) was reduced to Cr(III) while the valence state of the iron core is unchanged. Fe K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) and X-ray diffraction measurements also indicate no detectable transformation of the Fe3O4 core occurs during Cr(VI) adsorption and reduction. Thus, suggesting HA on the surface of HA-Fe3O4 is responsible for the reduction of Cr(VI) to Cr(III). The functional groups associated with HA act as ligands leading to the Cr(III) complex via a coupled reduction complexation mechanism. Cr K-edge EXAFS demonstrates the Cr(III) in the Cr-loaded HA-Fe3O4 materials has six neighboring oxygen atoms likely in an octahedral geometry with average bond lengths of 1.98 angstrom. These results demonstrate that easily separable HA-Fe3O4 particles have promising potential for removal and detoxification of Cr(VI) in aqueous media.